FIELD OF THE INVENTION
This invention relates to a hysteretic energy absorber.
There are circumstances in which it is desired to decrease the application of energy to a body or structure. In some circumstances this may be done by springs, but only when the elastic restoration of the energy can be dealt with. Various devices such as shock absorbers or viscous dampers are used when for some reason the energy must not be restored.
A particularly troublesome situation arises in preventing the cyclic forces imposed by earthquakes from damaging buildings and their contents. The present invention arose in the first place as a means of providing a damper to be connected between the base of a structure and the foundations below the structure. The structure was to be supported by a system, interposed between its base and its foundations, which allowed substantially free horizontal motion of the base. A combination of a flexible base-support system and a set of large-capacity energy absorbers of suitable characteristics would provide, for most structures, a substantial measure of protection from severe earthquake forces, while at the same time preventing frequent troublesome motions.
Common types of energy absorber are not satisfactory. In the first place, those which would absorb enough energy to protect a building in a severe earthquake would be so big as to be unusable. Velocity dampers are unsatisfactory, since they would do nothing to prevent the slow movement of the building. Hydraulic dampers might be made big enough, but they would allow drift from, for instance, wind loads, they would be expensive, and their upkeep would demand frequent attention.